Admission Heart Rate Variability is Associated with Fever Development in Patients with Intracerebral Hemorrhage

Fever is associated with worse outcome after intracerebral hemorrhage (ICH). Autonomic dysfunction, commonly seen after brain injury, results in reduced heart rate variability (HRV). We sought to investigate whether HRV was associated with the development of fever in patients with ICH.

We prospectively enrolled consecutive patients with spontaneous ICH in a single-center observational study. We included patients who presented directly to our emergency department after symptom onset, had a 10-second electrocardiogram (EKG) performed within 24 h of admission, and were in sinus rhythm. Patient temperature was recorded every 1-4 h. We defined being febrile as having a temperature of ≥ 38 °C within the first 14 days, and fever burden as the number of febrile days. HRV was defined by the standard deviation of the R-R interval (SDNN) measured on the admission EKG. Univariate associations were determined by Fisher's exact, Mann-Whitney U, or Spearman's rho correlation tests. Variables associated with fever at p ≤ 0.2 were entered in a logistic regression model of being febrile within 14 days.

There were 248 patients (median age 63 [54-74] years, 125 [50.4%] female, median ICH Score 1 [0-2]) who met the inclusion criteria. Febrile patients had lower HRV (median SDNN: 1.72 [1.08-3.60] vs. 2.55 [1.58-5.72] msec, p = 0.001). Lower HRV was associated with more febrile days (R = - 0.22, p < 0.001). After adjustment, lower HRV was independently associated with greater odds of fever occurrence (OR 0.92 [95% CI 0.87-0.97] with each msec increase in SDNN, p = 0.002).

HRV measured on 10-second EKGs is a potential early marker of parasympathetic nervous system dysfunction and is associated with subsequent fever occurrence after ICH. Detecting early parasympathetic dysfunction may afford opportunities to improve ICH outcome by targeting therapies at fever prevention.